x86: Add tests for Guest Processor Event Based Sampling (PEBS)

This unit-test is intended to test the KVM's support for
the Processor Event Based Sampling (PEBS) which is another
PMU feature on Intel processors (start from Ice Lake Server).

If a bit in PEBS_ENABLE is set to 1, its corresponding counter will
write at least one PEBS records (including partial state of the vcpu
at the time of the current hardware event) to the guest memory on
counter overflow, and trigger an interrupt at a specific DS state.
The format of a PEBS record can be configured by another register.

These tests cover most usage scenarios, for example there are some
specially constructed scenarios (not a typical behaviour of Linux
PEBS driver). It lowers the threshold for others to understand this
feature and opens up more exploration of KVM implementation or
hw feature itself.

Signed-off-by: Like Xu <likexu@tencent.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/r/20221102225110.3023543-23-seanjc@google.com